Cocaine abuse among methadone-maintained patients is a problem for which there is currently no effective treatment. One difficulty in demonstrating efficacy for pharmacotherapeutic agents in this group of patients may be that cocaine-abusing methadone subjects typically enrolled in clinical trials possess low motivation to stop abusing cocaine. In the proposed double-blind study of mazindol we plan to address the issue of patient motivation by enrolling patients at two different stages of abstinence initiation, and by investigating the interaction between these stages and two different doses of mazindol. A sample of 198 methadone-maintained subjects with documented cocaine dependence will be stratified on the basis of stage of abstinence initiation: (a) patients abusing cocaine at time of entry into the study, and (b) patients abstinent from cocaine use for between one and four weeks. They will then be randomized to receive either low-dose mazindol (l mg), higher dose mazindol (8 mg), or placebo for 12 weeks. The specific aims of the study are: to determine if mazindol (1 mg or 8 mg) is more effective than placebo for the treatment of cocaine dependence; to determine if patients at different stages of abstinence initiation (currently using vs. abstinent for 1-4 weeks) are differentially responsive to treatment; to determine if there is a mazindol by stage of abstinence initiation interaction; to characterize patients at different stages of abstinence initiation at entry into the study, to assess changes that occur along various dimensions with treatment; and to explore other potential predictors of treatment outcome (e.g., Antisocial Personality Disorder, depression, sex). Cocaine use, verified by three times weekly urine toxicology screens will be the primary outcome measure. Other measures include: self-reported frequency and amount of cocaine use, cue reactivity, stage of change, self- representation, depression, and composite scores on the Addiction Severity Index. Follow-up data will be collected at six months post- treatment.